1. Field of the Invention
The present invention relates to a method of generating a low frequency electrical stimulus signal to provide an electrical stimulus to a biological body, and also to an apparatus for generating a low frequency electrical stimulus signal.
2. Description of Prior Art
It is known that when audible, or hearing stimulus is provided to a biological body by, for instance, playing classical music, curative effects for pain, shoulder discomfort, unpleasant feeling and so on can be achieved since the pleasantness or unpleasantness felt by the biological body is based upon the experimental conception, or the body's concentration is directed to other matters than pain and unpleasant feelings. Similarly, it is also known that when electric stimulus (skin, or percutaneous stimulus) is given to a biological body, the pain, shoulder discomfort and other unpleasant feelings can be relaxed, or cured.
According to experimental studies, it is also known that a biological body can feel more refresh stimulus, which can achieve higher curative effects, under the condition that a stimulus given at a higher rate per unit of time to the biological body is better than a stimulus which is given to the body at a lower rate per unit of time, and the stimulus regularly given is better than the stimulus irregularly given.
Based upon the above-described facts, various curative methods have been developed to reduce pain by utilizing the above stimulus.
For a conventional electric stimulus signal generating technique, there has been proposed, for instance, a method of producing an electric stimulus signal, the pulse repetition frequency of which is not varied in accordance with a lapse of time, and giving such a stimulus signal to a biological body, especially to the body's sympathetic nerves and parasympathetic nerves. Moreover, a conventional electric stimulus signal generating apparatus is known from, for example, Japanese patent publication No. 56-5543 (referred to as a "printed publication I") and Japanese utility model publication No. 56-22921 (referred to as a "printed publication II").
The first reference describes such a technique in accordance with the 1/f fluctuation theory, i.e., the signal of music being analyzed in the frequency spectrum, and the power spectrum density of the analyzed signal being inversely proportional to the frequency, while the frequency of the electric stimulus signal is changed in a relatively long time range from 0.5 to 4 seconds within a range from 10 to 100 Hz, for producing the electric stimulus signal.
On the other hand, the second reference describes a technique of recording the pulse repetition frequency of the electric stimulus signal and also the irregular pulse pattern when the generating duration time of the same pulse repetition is varied, and reproducing the recorded data from the recording medium in accordance with the 1/f fluctuation theory.
Since, as is known in this field, the tempo of music is synchronized with the nerve and furthermore tissue and cells, the effects to reduce pain can be emphasized. Accordingly, this effect can be realized in that if the sound volume level (i.e., sound pressure level) is used as the sound information, the percutaneous stimulus can be provided to a biological body in synchronism with the tempo of the music.
However, since according to the above-described conventional technique, the percutaneous stimulus is provided to a biological body in accordance with the frequency of the 1/f fluctuation theory, it is practically difficult to adjust this stimulus with the tempo of the music.
Moreover, it is known in this field that when the audible, or hearing stimulus such as music and sounds, and the percutaneous stimulus (electric stimulus) reflecting the sound information are combined and provided to a biological body, a greater curative effect to reduce the mental pain can be expected as compared with a single stimulus. The curative effect may be further emphasized when both the hearing stimulus and the electric stimulus are given to a biological body in substantially real time.
However, according to the conventional techniques, neither method can provide both stimulus to a biological body in real time. Accordingly, since the electric stimulus is given to a biological body even when the music is under rest condition (in case of rest mode and lower sound pressure), this stimulus is not matched with the experimental mental reduction of unpleasantness of a biological body. As a result, the biological body feels this stimulus as the continuous variation of mere stimulus patterns, so that there is not as much curative effect to reduce the pain.